This invention relates to multilamp photoflash units and, in particular, to a more compact, cost-efficient array of photoflash lamps, having a secured housing enclosure with enhanced containment strength.
Previous multilamp photoflash units having a horizontally disposed base are represented by the electrically fired four-lamp array referred to as a flashcube, such as described in U.S. Pat. No. 3,327,105, the percussively ignited four-lamp array referred to as a magicube, such as described in U.S. Pat. No. 3,730,669, and the electrically sequenced ten-lamp array referred to as a flash bar, such as described in U.S. Pat. No. 3,857,667. In each of these arrays, the lamps are supported from a generally horizontal plastic base member with the tubular lamp envelopes oriented vertically. Enclosure of the package construction is provided by a transparent plastic cover member having four vertical side walls and a horizontal top wall. A multicavity reflector assembly is disposed about the lamps, and then the transparent cover member is placed over the array of lamps and reflectors and attached to the base member so as to provide an enclosed unit. In the case of the flashcube and flash bar, attachment of the plastic cover to the plastic base member is accomplished by ultrasonically welding the periphery of the cover member about a lip formed along the outer edges of the base member. In the case of the magicube, the preferred method is to employ a high intensity light source to produce heat energy which is absorbed by a darkly colored base member to thereby melt-seal the periphery of the cover member about a lip formed along the outer edges of the base member.
Another type of currently marketed photoflash unit, referred to as a flip flash, comprises a vertically planar array of eight or ten lamps which are ignited by sequentially applied high-voltage firing pulses. The overall construction of the flip flash unit comprises a substantially planar rear housing member and a front housing member in the form of a rectangular concavity, both housing members being formed of a plastic material. Sandwiched between the front and rear housing members, in the order named, are the flashlamps, a multicavity reflector assembly, an insulating sheet, a printed circuit board, and an indicia sheet. According to one embodiment, such as described in U.S. Pat. No. 4,047,015, the front and rear housing members are attached together by interlocking latch means molded in the edges thereof. Use of mechanical latching alone was found to be inadequate for product integrity, as twisting the array or dropping the array several feet onto a hard surface was found to be sufficient to break it open. Accordingly, the seam about the adjoining peripheries of the front and rear housing members is also ultrasonically welded together. In another embodiment of the flip flash array, for example as described in U.S. Pat. No. 4,133,023, the front and rear housing members are joined solely by the welded seam about their peripheries.
According to another embodiment of a planar array of eight flashlamps, for example, as illustrated in German Offenlegungsschrift No. 2629041, published Jan. 27, 1977, the unit has a bathtub-shaped rear housing member and a substantially planar transparent cover member. The planar cover is attached to the rear housing member by two posts projecting from the central portion of the cover in the upper and lower halves thereof, normal to the plane of the cover, which fit into and pass through respective openings in a pair of inwardly protruding bosses in the rear housing member. The ends of the posts projecting through the back of the rear housing are then reshaped with heat to form retaining lugs or rivet heads. The perimeter of the rear housing and planar cover is unsealed except for small mechanical latches at each end provided by the fit of the small cover projections into recesses in the rear housing.
U.S. Pat. No. 4,245,280 describes a more compact, cost-efficient photoflash unit construction which comprises a plurality of electrically ignitable flashlamps disposed in a vertical linear array on a strip-like printed circuit board. The assembly comprising the lamps mounted on the printed circuit strip is located within the longitudinal channel of an elongated housing member having outer flanges with reflector surfaces adjacent to the lamps. A light-transmitting cover panel is mounted to the housing member so as to enclose the flashlamps in the channel. To provide structural rigidity, the cover has rectangular corner posts at each end and a transverse web at the center which engage slots in the housing and are secured by ultrasonic welding. The longitudinal edges are secured by a plurality of cylindrical posts along each side of the cover which fit into matching holes in the housing and have rivet heads formed on the ends as provided by ultrasonic heating and pressure.
In a unidirectional linear photoflash array described in U.S. Pat. No. 3,473,880 of Wick, the lamps are connected to a printed circuit board which comprises the rear housing of the unit and includes reflector cavities. A separate transparent panel of plastic sheet material is then glued or otherwise affixed to the front of the rear housing so as to enclose the lamps.
A copending patent application Ser. No. 181,936, filed concurrently herewith and assigned to the present assignee, describes a compact, cost-efficient photoflash unit comprising a horizontal linear array of flashlamps enclosed within a one-piece housing member having a light-transmitting front portion folded over a back portion containing a plurality of lamp-receiving cavities in which respective lamps are disposed. The housing is a formed sheet of plastic film having a linear fold disposed horizontally along the top of the array of cavities, which are selectively aluminized to provide a reflective coating on the cavity surfaces. A pair of lead-in wires from each of the lamps are connected to conductive circuit patterns on one side of a printed circuit board sandwiched between a set of tabs which run along the bottom of the front and back portions of the housing. The housing tabs are to be secured together so as to retain the printed circuit board therebetween and enclose the lamps within the housing. The fold along the top of the housing provides longitudinal rigidity and enhanced joining strength at the top of the array enclosure; however, at the bottom, the use of prior art closure methods, such as heat, sonic sealing or adhesives, is less than desireable in this application. The tabs at the lower peripheral areas of the folded over plastic film housing are not thermally sealable to the typical phenolic printed circuit board, and adhesives or glue tend to be a messy production material and do not provide the maximized degree of containment strength particularly desireable for photoflash unit enclosures.